This invention relates to service station equipment and, more particularly, to a Stage II Vapor Recovery System.
When filling vehicle tanks with gasoline or other volatilizable fuel through dispensing nozzles of conventional (non-vapor recovery) systems, vapors from the gasoline or other volatilizable fuel within the vehicle tank escape to the atmosphere through the opening in which the spout of the nozzle is inserted and may pollute the air. Large numbers of vehicles being fueled at service stations over a period of time can result in a substantial emission and accumulation of hydrocarbons into the atmosphere. On average, there are about four grams of hydrocarbons in a gallon of vapor mixture displaced during fueling. In terms of hydrocarbon air contaminants, these four grams of hydrocarbons, are about 20% of the emissions of newer vehicles. Stage II vapor recovery is a strategy to capture the vapors released during fueling of vehicles so as to minimize atmospheric hydrocarbon vapor emissions which when exposed to sunlight can react with other air contaminants to create ozone.
Historically, stage II vapor recovery is a result of substantial well-founded concerns of the public and various government agencies, such as the U.S. Environmental Protection Agency (EPA), over the quality of air in many population centers. In response to these concerns, the EPA and other government agencies have established a set of air quality standards.
In order to attain these air quality standards, stage II vapor recovery systems have been recommended or mandated by many regulatory bodies of federal, state, county, municipal and local governments, such as environmental agencies, air resource boards, and health departments. In stage II vapor recovery systems, fuel is dispensed into vehicle tanks at service stations and, simultaneously, a substantial amount of the refueling hydrocarbon vapor emissions are returned to the storage tanks in the service stations. Vapor recovery systems can be classified in two categories: balanced pressure systems and vacuum assist systems.
In balanced pressure systems, an elastomeric boot or other positive sealing arrangement is provided to engage and seal the fill opening or filler pipe of the vehicle tank during fueling. The interior of the boot is connected through a vapor return conduit to the underground storage tank so that hydrocarbon vapors emitted during fueling naturally flow to the storage tank to maintain the pressure balance between the vehicle tank and the storage tank.
The vacuum assist system differs from the balanced pressure system because it does not require a tight sealing boot or some other positive sealing arrangement with the fill opening or filler pipe of the vehicle tank. Instead, the vapor return conduits are connected through a vapor pump, vacuum pump or other vacuum inducing assist device to collect and transport the vapors emitted during fueling to the storage tanks.
In stage II vapor recovery systems, a natural phenomena that occurs is that as warm gasoline vapors from the vehicle tank return through the vapor return hose of the island dispenser, a certain portion of the vapors condense into liquid because of changes in temperature and pressure. These condensed liquids collect in the low point of the vapor return hose and, if not removed, can accumulate and block the vapor passageway. Such blockage can render the stage II vapor recovery system ineffective by precluding the return of vehicle tank vapors to the storage tanks. Furthermore, such collected condensate, if not properly controlled and removed, may spill onto to the clothing and shoes of customers, creating an undesirable odor as well as a potentially flammable and dangerous condition.
Various suggestions have been proposed to overcome this condensate problem. These suggestions have generally not been satisfactory from a technical and economic viewpoint and have not been met with consumer enthusiasm. One suggestion has been to decrease the size of the vapor return hoses. Such a suggestion is generally not practicable for most service stations. Dispensing equipment manufacturers, such as Gilbarco and Dayco, have suggested add-on devices to the dispenser fuel hose which create a low pressure area in the vapor return hoses. These add-on devices, however, are expensive, bulky, and subject to leakage, as well as undesirably reducing the delivery flow rate of fuel to the vehicle tank by as much as 20%. Furthermore, customers don't like the add-on systems because it takes longer to fill their vehicle tanks. Moreover, service station managers and proprietors generally do not like these add-on devices because they are inefficient and preclude servicing as many customers per hour as systems not using these devices.
Over the years a variety of nozzles and other items of service station equipment have been developed or suggested. These prior art nozzles and prior art items of service station equipment have been met with varying degrees of success, but have generally not solved the preceding problems. Typifying these prior art nozzles and prior art service station equipment items are those found in U.S. Pat. Nos. 2,527,760; 2,908,299; 3,845,792; 3,016,928; 3,756,291; 3,763,901; 3,805,857; 3,826,291; 3,830,267; 3,835,899; 3,840,055; 3,845,792; 3,850,208; 3,874,427; 3,913,633; 3,914,095; 3,915,206; 3,918,932; 3,941,168; 3,952,781; 3,981,335; 3,989,072; 3,990,490; 4,441,533; 4,057,086; 4,058,147; 4,068,687; 4,082,122; 4,090,525; 4,095,626; 4,098,308; 4,111,244; 4,131,140; 4,133,355; 4,143,689; 4,153,073; 4,157,104; 4,166,485; 4,167,957; 4,197,883; 4,199,012; 4,202,385; 4,203,478; 4,204,563; 4,213,488; 4,223,706; 4,244,403; 4,245,681; 4,253,503; 4,256,151; 4,258,760; 4,295,504; 4,295,802; 4,306,594; 4,310,033; 4,320,788; 4,336,830; 4,343,337; 4,351,375; 4,372,353; 4,429,725; 4,441,533; 4,469,149; 4,497,350; 4,502,516; 4,557,302; 4,566,504; 4,570,686; 4,593,729; 4,687,033; 4,825,914; 4,827,987; 4,984,612; and U.S. Pat. No. RE. 31,882; and in Swiss Patent Number 385,053; and U.K. Patent publication 2,016,417A.
It is, therefore, desirable to provide an improved stage II vapor recovery system which overcomes most, if not all, of the preceding problems.